Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
Phased array antenna devices comprise a group of radiating elements that are fed by relative phases of the respective microwave signals. Its radiation pattern can be electrically steered by changing the relative phases of the signals without mechanically moving the antenna, which has been found many applications due to its agility and reliability. Recently, there has been an increasing attention applied to optically controlled beamforming techniques. For example, see Stulemeijer, F. E. van Vliet, K. W. Benoist, D. H. P. Maat, and M. K. Smit, “Compact photonic integrated phase and amplitude controller for phased-array antennas,” IEEE Photonics Technology Letters, vol. 11, pp. 122-124, January 1999.
Utilising photonic technologies in the construction of phased array antennas has advantages such as a wide bandwidth, low loss, compact size, remote antenna feeding and immunity to electromagnetic interference. In many radar and satellite communication systems that do not require large bandwidths, the phase shift phased array beamforming network is desirable because it has a compact architecture and elegant layout.
A significant element in photonic beamformers is a wideband photonic microwave phase shifter, which is required to have independent and continuous phase controls ranging from 0 to 2π for each array element with a satisfactory phase accuracy. It is also preferable to be constructed with all-optical methods to fully exploit the capacity of photonics without limitations of electronics.